Tractor

ABSTRACT

The present invention aims at a tractor which can easily perform an assembling operation and a maintenance operation of a PTO transmission mechanism. According to the present invention, a PTO casing which incorporates a PTO transmission mechanism therein is detachably mounted on a rear portion of a transmission casing and, at the same time, the PTO casing is mounted in a state that a front portion thereof is housed in the inside of the transmission casing. By mounting the PTO casing which incorporates the PTO transmission mechanism therein on the rear portion of the transmission casing in this manner, it is possible to easily perform the assembling operation and the maintenance operation of the PTO transmission mechanism. Further, by mounting the PTO casing in a state that the front portion thereof is housed in the inside of the transmission casing, it is possible to miniaturize the transmission casing (make the transmission casing compact).

TECHNICAL FIELD

The present invention relates to a tractor.

BACKGROUND ART

Conventionally, as a type of tractor, there has been known a tractor inwhich an engine is mounted on a front portion of a vehicle body frame, adriver's part is provided at a position behind the engine, atransmission casing is provided at a position below a driver's seatmounted in the driver's part, a PTO transmission mechanism is mounted inthe inside of the transmission casing, and a PTO shaft which isinterlockingly connected with the PTO transmission mechanism projectsrearwardly from a rear wall of the transmission casing (see JapanesePatent Laid-open Hei7(1995)-232570, for example).

Further, as a type of tractor, there has been known a tractor in which aproximal end portion of a lift arm is pivotally mounted on an upperportion of the transmission casing, a lift cylinder mounting portion isprovided in a state that the lift cylinder mounting portion projectsrearwardly from a rear wall of the transmission casing, and a liftcylinder which extends or contracts in the vertical direction isinterposed between the lift cylinder mounting portion and a middleportion of the lift arm (see Japanese Patent Laid-openHei9(1997)-109710, for example).

However, in the above-mentioned tractor, since the PTO transmissionmechanism is mounted in the inside of the transmission casing, it isnecessary to perform the assembling operation and the maintenanceoperation of the PTO transmission mechanism in the inside of thetransmission casing whereby there arises a drawback that the operationbecomes cumbersome and, at the same time, there also arises a drawbackthat the transmission casing per se is large-sized in the rearwarddirection.

Further, in the above-mentioned latter tractor, since the lift cylindermounting portion is provided in a state that lift cylinder mountingportion projects rearwardly from the rear wall of the transmissioncasing, the adjustment to arrange the lift cylinder which is interposedbetween the lift cylinder mounting portion and a middle portion of thelift arm vertically or substantially vertically becomes cumbersome.

That is, since the transmission casing becomes large-sized in therearward direction, when the lift cylinder is simply interposed betweenthe lift cylinder mounting portion which is provided in a state that thelift cylinder mounting portion projects in the rearward direction fromthe rear wall and the middle portion of the lift arm, the lift cylinderassumes an inclined posture. Eventually, there arise drawbacks that alarge lift cylinder having a long stroke becomes necessary and, at thesame time, a power loss is generated.

Accordingly, by pivotally mounting a proximal end portion of the liftarm as close as possible to a rear end portion of the transmissioncasing or by elongating an arm length of the lift arm, the posture ofthe lift cylinder may be arranged vertically or substantiallyvertically. However, the arrangement requires a cumbersome operationthat the arrangement must be performed only after confirming the changeof strength of the pivotal mounting structure of the proximal endportion of the lift arm, the kinetic change (the change of the moment)brought about by the change of the arm length of the lift arm, change ofthe elevation and lowering locus of a working machine which is connectedto the lift arm and the like.

DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to provide atractor which is characterized in that a PTO casing which incorporates aPTO transmission mechanism therein is detachably mounted on a rearportion of a transmission casing and, at the same time, the PTO casingis mounted in a state that a front portion thereof is housed in theinside of the transmission casing.

Further, a proximal end portion of the lift arm is pivotally mounted onan upper portion of the transmission casing, a lift cylinder mountingportion is formed on a lower portion of a side wall of the PTO casing,and a lift cylinder which performs an extension-and-contraction movementin the vertical direction is interposed between the lift cylindermounting portion and a middle portion of the lift arm.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a side view of a tractor according to the present invention;

FIG. 2 is a side view of a clutch part and a transmission part;

FIG. 3 is a cross-sectional explanatory side view of the clutch part andthe transmission part;

FIG. 4 is a cross-sectional explanatory side view of the clutch part;

FIG. 5 is a cross-sectional explanatory side view of a main transmissionpart;

FIG. 6 is a cross-sectional explanatory back view of the maintransmission part;

FIG. 7 is an enlarged cross-sectional explanatory back view of an upperportion of the main transmission part;

FIG. 8 is a cross-sectional explanatory side view of a sub transmissionpart and a PTO transmission part;

FIG. 9 is a cross-sectional plan explanatory view of a differentialmechanism;

FIG. 10 is a back view of a PTO transmission part;

FIG. 11 is a back view with a part broken away of the PTO transmissionpart;

FIG. 12 is a cross-sectional side view of a clutch part of asingle-clutch specification;

FIG. 13 is a cross-sectional explanatory side view of a sub transmissionpart as another embodiment; and

FIG. 14 is a cross-sectional explanatory side view of the subtransmission part as another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

The mode for carrying out the invention is explained hereinafter.

That is, in a tractor according to the present invention, a PTO casingwhich incorporates a PTO transmission mechanism therein is detachablymounted on a rear portion of a transmission casing and, at the sametime, the PTO casing is mounted in a state that a front portion thereofis housed in the inside of the transmission casing.

Further, a proximal end portion of the lift arm is pivotally mounted onan upper portion of the transmission casing, a lift cylinder mountingportion is formed on a lower portion of a side wall of the PTO casing,and a lift cylinder which performs an extension-and-contraction movementin the vertical direction is interposed between the lift cylindermounting portion and a middle portion of the lift arm.

Symbol A shown in FIG. 1 indicates the tractor according to the presentinvention. In the tractor A, the prime mover part 2 is mounted on a bodyframe 1, the transmission part 4 is interlockingly and contiguouslymounted on the prime mover part by way of a clutch part 3, a driver'sportion 5 is arranged on the transmission part 4 and, at the same time,a PTO transmission part 6 is detachably and interlockingly connectedwith a rear portion of the transmission part 4, while a pair of left andright front wheels 7, 7 are interlockingly connected to the transmissionpart below the above-mentioned body frame 1 by way of a front axlecasing (not shown in the drawing), a pair of left and right rear wheels9, 9 are interlockingly connected with the above-mentioned transmissionpart 4 by way of rear axle casings 8,8 (see FIG. 9). Numeral 10indicates a front portion guard frame, numeral 11 indicates a rearportion guard frame, numeral 12 indicates a top link for connecting aworking machine to the tractor, numeral 13 indicates a lower link forconnecting the working machine to the tractor, and numeral 14 indicatesa working-machine connecting member.

In the prime mover part 2, as shown in FIG. 1, an engine 15 and the likeare mounted on the body frame 1, wherein the engine 15 and the like arecovered with a hood 16 in a state that the hood can be opened or closed.

The clutch part 3, as shown in FIG. 2 to FIG. 4, rotatably supports aninner-and-outer duplicate drive shaft body 18 which extends in thelongitudinal direction in the inside of a clutch housing 17, wherein theinner-and-outer duplicate drive shaft body 18 is formed of an innerdrive shaft 19 which extends in a longitudinal direction and acylindrically-shaped outer drive shaft 20 which is rotatably fitted onan outer periphery of the inner drive shaft 19.

Further, out of the inner drive shaft 19 and the outer drive shaft 20, aproximal portion (a front end portion) of the inner drive shaft 19 isinterlockingly connected with the engine 15 by way of a traveling clutch21 and, at the same time, a distal end portion (a rear end portion) ofthe inner drive shaft 19 is interlockingly connected with atraveling-system power transmission mechanism 22 described later.Further, a proximal portion (front end portion) of the outer drive shaft20 which constitutes another drive shaft is interlockingly connectedwith the engine 15 by way of a PTO clutch 22 and, at the same time, adistal end portion (a rear end portion) of the outer drive shaft 20 isinterlockingly connected with a PTO-system power transmission mechanism52 described later.

Here, a front-end-peripheral portion of the main transmission casing 53of the transmission part 4 described later is detachably connected to arear-end-peripheral portion of the clutch housing 17. In theabove-mentioned inner-and-outer duplicate drive shaft body 18, adistal-end portion thereof is pivotally supported on a bearing 24 whichis arranged at a front portion in the inside of the clutch housing 17,while a rear-end portion thereof is pivotally supported on a bearing 25which is arranged on a front portion in the inside of the maintransmission casing 53.

Further, a rear wall 27 having an opening portion 26 in the centerportion thereof is formed on an inner peripheral portion of a rear endof the clutch housing 17. A cylindrical support body 28 which extends inthe longitudinal direction is mounted on the rear wall 27 in a statethat the cylindrical support body 28 passes through the opening portion26. An outer-peripheral surface of the middle portion of theabove-mentioned inner-and-outer duplicate drive shaft body 18 issupported by the cylindrical support body 28.

Then, in the cylindrical support body 28, a diameter of a front portion28 a thereof which is positioned in the inside of the clutch housing 17is reduced and, on the other hand, a diameter of a rear portion 28 bwhich is positioned in the inside of the main transmission casing 53 isenlarged. Amounting flange member 28 c is formed on an outer-peripheralsurface of the rear portion 28 b and the mounting flange member 28 c isbrought into contact with a rear surface of the rear wall 27 of theclutch housing 17 from behind and, at the same time, is mounted on therear wall 27 using a mounting bolt 29.

Further, the inner drive shaft 19 is formed in a split manner into afront split drive shaft member 30 and a rear split drive shaft member 31and, at the same time, both of the split drive shaft members 30, 31 areinterlockingly connected with each other in the inside of the outerdrive shaft 20. A split position (interlocking connection portion)between the front split drive shaft member 30 and the rear split driveshaft member 31 is arranged in the vicinity of the connection portion ofthe clutch housing 17 and the main transmission casing 53, that is, inthe inside of the rear portion 28 b of the cylindrical support body 28.

Further, a distal-end portion of the front split drive shaft member 30and a proximal-end portion of the rear split drive shaft member 31 aredetachably and interlockingly connected with each other by spigotfitting.

That is, a fitting projection member 30 a is mounted on a distal-endsurface of the front split drive shaft member 30 in a state that thefitting projection member 30 a projects in the rearward direction, whilea proximal-end-side fitting recessed portion 31 a is formed in aproximal-end surface of the rear split drive shaft member 31. Theabove-mentioned fitting projection member 30 a is fitted in the insideof the proximal-end-side fitting recessed portion 31 a by spigot fittingand, at the same time, a cylindrical connection body 32 having an axisthereof directed in the longitudinal direction is engaged with a splinegroove 30 b which is formed in an outer-peripheral surface of thedistal-end portion of the front split drive shaft member 30 and a splinegroove 31 b which is formed in an outer-peripheral surface of theproximal-end portion of the rear split drive shaft member 31 by splinefitting.

The outer drive shaft 20 has a front portion 20 a thereof formed with asmall diameter along the outer peripheral surface of the inner driveshaft 19 and a rear portion 20 b thereof formed with a large diameteralong the outer peripheral surface of the above-mentioned cylindricalconnection body 32 and, bearings 33, 34 are interposed between an outerperipheral surface of the rear portion 20 b and an inner peripheralsurface of the rear portion 28 b of the cylindrical support body 28.

Further, a distal-end portion of the outer drive shaft 20 extends in therearward direction than the rear end of the cylindrical support body 28and a PTO drive gear 20c is integrally formed on the outer peripheralsurface of the distal-end portion of the outer drive shaft 20. Numeral35 indicates a PTO drive gear support bearing.

In this manner, the inner drive shaft 19 is formed in a split mannerinto the front split drive shaft member 30 and the rear split driveshaft member 31 and, at the same time, both of the drive shaft members30, 31 are interlockingly connected with each other in the inside of theouter drive shaft 20. Accordingly, compared to a conventional technique,that is, a technique in which a distal-end portion of an inner driveshaft is extended to the position behind the distal-end portion of theouter drive shaft and the distal-end portion of the inner drive shaft iscoaxially and interlockingly connected with a proximal-end portion of aPTO-system input shaft in an abutted manner by way of a cylindricalshaft coupling, even when the clutch housing 17 and the maintransmission casing 53 are connected to each other in the longitudinaldirection and the inner-and-outer duplicate drive shaft body 18 passesthrough the inside of the clutch housing 17 and the main transmissioncasing 53, it is possible to overcome the drawback that the maintransmission casing 53 becomes elongated or large-sized in thelongitudinal direction.

Further, it is possible to facilitate an assembling operation when theclutch housing 17 and the main transmission casing 53 are connected asan assembly, and a maintenance operation which is performed afterreleasing the connection or the like.

Still further, since the split position between the front split driveshaft member 30 and the rear split drive shaft member 31 of the innerdrive shaft 19 is arranged in the vicinity of the connection portion ofthe clutch housing 17 and the main transmission casing 53, it ispossible to make a width of the main transmission casing 53 small in thelongitudinal direction thus providing a compact body and, at the sametime, it is possible to make a width of the assembling unit of the maintransmission casing 53 small in the longitudinal direction thusrealizing the reduction of the distribution cost of the assembling unit.As a result, a large number of units can be transferred at a time fromoutsourcing.

Here, the fitting projection member 30 a which is formed on thedistal-end portion of the front split drive shaft member 30 isdetachably and interlockingly connected to the inside of theproximal-end-side fitting recessed portion 31 a which is formed on theproximal-end portion of the rear split drive shaft member 31 by spigotfitting and hence, the front split drive shaft member 30 and the rearsplit drive shaft member 31 which are formed in a split manner can beassembled with high accuracy and can be interlockingly connected.

Further, a traveling cylindrical operating body 36 is longitudinallyslidably fitted over the outer-peripheral surface of the outer driveshaft 20 and the outer-peripheral surface of the cylindrical supportbody 28 and a proximal-end portion of a traveling clutch operating lever37 is interlockingly connected with a rear portion of the travelingcylindrical operating body 36, while a clutch operating member 36 a ismounted on a front-end peripheral portion of the traveling cylindricaloperating body 36 and the clutch operating member 36 a is arranged closeto a motion receiving arm 21 a of the traveling clutch 21 in a statethat the clutch operating member 36 a faces the motion receiving arm 21a of the traveling clutch 21 in an opposed manner. Numeral 38 is a leversupport shaft.

In this manner, when the traveling clutch operating lever 37 isrotatably manipulated, the traveling cylindrical operating body 36 isallowed to slide in the forward direction and the clutch operatingmember 36 a pushes the motion receiving arm 21 a and the motionreceiving arm 21 a is rotated so as to allow the traveling clutch 21 toperform a power cutting operation.

Further, a PTO cylindrical operating body 39 is longitudinally slidablyfitted on the outer-peripheral surface of the traveling cylindricaloperating body 36 and a proximal-end portion of the PTO clutch operatinglever 40 is interlockingly connected with the rear portion of the PTOcylindrical operating body 39, while a clutch operating member 39 a ismounted on a front-end-peripheral portion of the PTO cylindricaloperating body 39 and the clutch operating member 39 a is arranged closeto the motion receiving arm 22a of the PTO clutch 22 in a state that theclutch operating member 39 a faces the motion receiving arm 22 a of thePTO clutch 22 in an opposed manner. Numeral 41 is a lever support shaft.

In this manner, when the PTO clutch operating lever 40 is rotatablymanipulated, the PTO cylindrical operating body 39 is allowed to slidein the forward direction and the clutch operating member 39 a pushes themotion receiving arm 22 a and the motion receiving arm 22 a is rotatedso as to allow the PTO clutch 22 to be performed a power cuttingoperation.

With respect to the transmission part 4, as shown in FIG. 2 and FIG. 3,in the inside of the transmission casing 45 which is formed in acylindrical shape by extending the transmission casing 45 in thelongitudinal direction, a main transmission mechanism 46, a subtransmission mechanism 47 and a differential mechanism 48 aresequentially arranged from front to back and, at the same time, a creeptransmission part 49 is detachably mounted on the transmission casing 45and a creep transmission mechanism 50 which is formed on the creeptransmission part 49 is interlockingly connected with theabove-mentioned sub transmission mechanism 47 thus forming atraveling-system power-transmission mechanism 51 which can perform themain transmission, the sub transmission and the creep transmission.Further, a PTO-system power-transmission mechanism 52 is interposedbetween the above-mentioned outer drive shaft 20 and a PTO transmissionpart 6 described later.

Then, the transmission casing 45 is split in two, that is, the maintransmission casing 53 which incorporates the main transmissionmechanism 46 and the casing body 54 which incorporates the subtransmission mechanism 47 and the differential mechanism 48. In the maintransmission casing 53, a front-end-peripheral portion thereof isdetachably connected with the rear-end-peripheral portion of the clutchhousing 17 using a connection bolt 56 a and, at the same time, in thecasing body 54, a front-end-peripheral portion thereof is detachablyconnected with the rear-end-peripheral portion of the main transmissioncasing 53 by way of a support wall forming body 55 using a connectionbolt 56 b.

Here, the constitutions of the main transmission casing 53, the maintransmission mechanism 46, the casing body 54, the sub transmissionmechanism 47 and the differential mechanism 48 are explained in thisorder.

[Main Transmission Casing]

The main transmission casing 53 is, as shown in FIG. 5 and FIG. 6,formed in a cylindrical shape which extends in the longitudinaldirection and an inner support wall 57 is formed on an inner-peripheralsurface of the front portion thereof and interposes the maintransmission mechanism 46 between the inner support wall 57 and theabove-mentioned support wall forming body 55 thus enabling the advancingtransmission manipulation and retracting changeover manipulation havingplural stages (5 stages in this embodiment) by the main transmissionmechanism 46.

[Main Transmission Mechanism]

In the main transmission mechanism 46, as shown in FIG. 5 and FIG. 6, adistal-end portion (rear-end portion) of the rear split drive shaftmember 31 is supported on a center portion of the inner support wall 57by way of the above-mentioned bearing 25. A fifth-speed gear 31 c isintegrally formed on an outer-peripheral surface of the distal-endportion of the rear split drive shaft member 31 which is positionedbehind the bearing 25 and, at the same time, a distal-end-side fittingrecessed portion 31 d is formed on a rear-end surface of the rear splitdrive shaft member 31. A fitting projection member 58 a which isprojected in the more frontward direction than a proximal-end surface(front-end surface) of a main-transmission main shaft 58 which extendsin the longitudinal direction is fitted in the distal-end-side fittingrecessed portion 31 d in a state that the fitting projection member 58 ais rotatable about an axis thereof, while the distal-end portion(rear-end portion) of the main-transmission main shaft 58 is supportedon the center portion of the support wall forming body 55 in a statethat the distal-end portion of the main-transmission main shaft 58 isrotatable about an axis thereof by way of a bearing 59.

Then, on the main-transmission main shaft 58, fourth-speed, third-speed,second-speed and first-speed gears 60, 61, 62, 63 and a retractingchangeover gear 64 are sequentially mounted from the proximal-endportion side to the distal-end portion side in a state that the fourth,third, second, first-speed gears 60, 61, 62, 63 and the retractingchangeover gear 64 are arranged in a spaced-apart manner in thelongitudinal direction coaxially and rotatably around theouter-peripheral surface of the main-transmission main shaft 58.

Further, on the main-transmission main shaft 58, a third transmissionbody 65 which is arranged between the fifth-speed gear 31 c and thefourth-speed gear 60, a second transmission body 66 which is arrangedbetween the third-speed gear 61 and the second-speed gear 62, and afirst transmission body 67 which is arranged between the first-speedgear 63 and the retracting changeover gear 64 are mounted.

Here, the respective transmission bodies 65, 66, 67 include shaft-sideinterlocking connection members 65 a, 66 a, 67 a which areinterlockingly connected to the main-transmission main shaft 58, 58,front/rear-gear-side interlocking connection members 65 b, 65 c, 66 b,66 c, 67 b, 67 c which are interlockingly connected with the respectiveneighboring gears in the fore-and-aft directions, and slide connectionmembers 65 d, 66 d, 67 d which are engaged by spline fitting in aslidable manner in the axial direction between the respective shaft-sideinterlocking connection members 65 a, 66 a, 67 a and the respectivegear-side interlocking connection members 65 b, 65 c, 66 b, 66 c, 67 b,67 c.

Then, the respective slide connection members 65 d, 66 d, 67 d areslidably manipulated to assume any one of a neutral position, a frontslide transmission position and a rear slide transmission position. Thatis, at a neutral position, the respective slide connection members 65 d,66 d, 67 d are positioned on the respective shaft-side interlockingconnection members 65 a, 66 a, 67 a, at a front slide transmissionposition, the respective slide connection members 65 d, 66 d, 67 dinterlockingly connects the respective shaft-side interlockingconnection members 65 a, 66 a, 67 a and the front-gear-side interlockingconnection members 65 b, 66 b, 67 b after being slidably moved and arepositioned between the shaft-side interlocking connection members 65 a,66 a, 67 a and the front-gear-side interlocking connection members 65 b,66 b, 67 b and, at a rear slide transmission position, the respectiveslide connection members 65 d, 66 d, 67 d interlockingly connect therespective shaft-side interlocking connection members 65 a, 66 a, 67 aand the rear-gear-side interlocking connection members 65 c, 66 c, 67 cafter being slidably moved and is positioned between the shaft-sideinterlocking connection members 65 a, 66 a, 67 a and the rear-gear-sideinterlocking connection members 65 c, 66 c, 67 c.

Further, a main transmission sub shaft 70 which extends in thelongitudinal direction is supported between the inner support wall 57and the above-mentioned support wall forming body 55 by way of thefront/rear bearings 68, 69. First, second, third transmission gearbodies 71, 72, 73 are coaxially and rotatably mounted on theouter-peripheral surface of the main transmission sub shaft 70.

Further, a front gear 71 a and a rear gear 71 b which are integrallyformed on the first transmission gear body 71 are meshed with thefifth-speed gear 31 c and the second-speed gear 60 respectively.Further, a front gear 72 a and a rear gear 72 b which are integrallyformed on the second transmission gear body 72 are meshed with thethird-speed gear 61 and the second-speed gear 62 respectively. Further,a front gear 73 a which is integrally formed on the third transmissiongear body 73 is meshed with the first-speed gear 63, while a rear gear73 b which is integrally formed on the third transmission gear body 73is meshed with the retracting changeover gear 64 by way of a countergear 74 whose shaft is supported on the support wall forming body 55.Numeral 75 indicates a counter gear support shaft and numeral 76indicates a shaft support body formed in the inside of the maintransmission casing 53.

Still further, as shown in FIG. 5 to FIG. 7, a slide body support shaft80 which extends in the longitudinal direction is extended between theinner support wall 57 and the above-mentioned support wall forming body55 in a state that the slide body support shaft 80 is slidable in thelongitudinal direction at a position right above the above-mentionedmain-transmission main shaft 58 and, at the same time, a leverinterlocking shaft 81 which extends in the longitudinal direction isextended in a state that the lever interlocking shaft 81 which extendsin the longitudinal direction is made parallel with a right sideposition of the slide body support shaft 80 and slidable in thelongitudinal direction. A distal-end portion of an engaging member 82which is formed in a state that the engaging member 82 projects in themore leftward direction than the front portion of the lever interlockingshaft 81 is engaged with an engaging member 83 which is mounted on thefront portion of the slide body support shaft 80, while an operationreceiving member 84 is mounted on the rear-end portion of the leverinterlocking shaft 81 which is extended to the inside of the casing body54. An operation member 85 a which is formed on the lower-end portion ofthe main transmission lever 85 is engaged with the operation receivingmember 84. Numeral 97 indicates an operation-receiving member mountingpin.

Then, as shown in FIG. 2, a tilting support body 86 is mounted on aceiling portion 54 c of the casing body 54 and, as shown in FIG. 6, alower portion of the main transmission lever 85 which extends in thevertical direction is supported on a tilting support member 87 mountedon the tilting support body 86 and hence, the main transmission lever 85is allowed to be tiltably manipulated in the longitudinal and thelateral directions. A lower end of the operation member 85 a which isformed on a lower-end portion of the main transmission lever 85 passesthrough the inside of a lever insertion hole 88 which is formed on theceiling portion 54 c and is engaged with the above-mentioned operationreceiving member 84. Numeral 89 indicates a lever neutral restoringspring.

Further, as shown in FIG. 5 and FIG. 7, in a middle portion of the slidebody support shaft 80, a slide restricting body 91 which is formed in aC-shape as viewed from back having a side opening portion 90 is fittedand, at the same time, a slide operation member 92 projects from theslide body support shaft 80 in the radial direction through the insideof the side opening portion 90.

Further, first, second, third slide bodies 95, 94, 93 are sequentiallymounted on a slide body support shaft 80 from back to front in a statethat the first, the second, the third slide bodies 95, 94, 93 areslidable in the axial direction and, at the same time, the third slidebody 93 is arranged in front of the slide restricting body 91, while thefirst, the second slide bodies 95, 94 are arranged behind the sliderestricting body 91.

Further, the respective slide bodies 95, 94, 93 are provided with bossportions 95 a, 94 a, 93 a which are slidably fitted on the slide bodysupport shaft 80, shift forks 95 b, 94 b, 93 b which are formed in astate that the shift forks 95 b, 94 b, 93 b are extended in the moredownward direction on the left and right side than the respective bossportions 95 a, 94 a, 93 a and slide operation receiving members 95 c, 94c, 93 c which are formed in a state that the slide operation receivingmember 95 c, 94 c, 93 c are extended from the respective boss portions95 a, 94 a, 93 a toward the slide restricting member 91.

Further, the respective shift forks 95 b, 94 b, 93 b of the first, thesecond, the third slide bodies 95, 94, 93 are interlockingly connectedwith the slide connection members 67 d, 66 d, 65 d of theabove-mentioned first, second, third transmission bodies 67, 66, 65respectively.

Further, in the respective slide operation receiving members 95 c, 94 c,93 c of the first, the second, the third slide bodies 95, 94, 93, theslide body support shaft 80 is rotated about an axis thereof so as torotate the slide operation member 92 and the slide restricting body 91in a given direction. Accordingly, the slide operation member 92 isengaged with one given slide operation receiving member and the slideoperation receiving member is slidably operated interlockingly with thelongitudinal slide of the slide body support shaft 80 and, at the sametime, either one of restricting members 91 a, 91 b which are mounted onthe slide restricting body 91 in a projecting manner is engaged with theother two slide operation receiving members and hence, it is possible torestrict both slide operation receiving members from being slidablyoperated interlockingly with the longitudinal slide of the slide bodysupport shaft 80. Numeral 96 indicates a restricting projection memberwhich is formed on the ceiling portion 54 c of the casing body 54 in asuspended manner for restricting the movement of the slide restrictingbody 91 in the axial direction.

The main transmission mechanism 46 is constituted in the above-mentionedmanner. The transmission manipulation (from first transmissionmanipulation to fifth transmission manipulation and retractingchangeover manipulation) of the main transmission mechanism 46 isexplained hereinafter.

(First Transmission Manipulation)

The main transmission lever 85 is rotatably manipulated in the rearwarddirection in an approximately vertically erected state and the rotarymanipulation force is transmitted to the slide body support shaft 80 byway of the operation member 85 a which is formed on a lower-end portionof the main transmission lever 85→the operation receiving member 84→thelever interlocking shaft 81→the engaging member 82→the engaging member83→the slide body support shaft 80 so as to allow the slide body supportshaft 80 to slide in the frontward direction.

Accordingly, the sliding force of the slide body support shaft 80 in thefrontward direction is transmitted to the shift fork 95 b by way of theslide operation member 92→the slide operation receiving member 95 c ofthe first slide body 95→the boss portion 95 a and, thereafter, the slideconnection member 67 d of the first transmission body 67 which isinterlockingly connected with the shift fork 95 b is slid from theneutral position to the front slide transmission position thusestablishing a state in which the shaft-side interlocking connectionmember 67 a and the front-gear-side interlocking connection member 67 bare interlockingly connected with each other.

As a result, the power transmitted from the engine 15 to the inner-sidedrive shaft 19 is transmitted to the main-transmission main shaft 58 byway of the front split drive shaft member 30→the rear split drive shaftmember 31→the fifth-speed gear 31 c→the front gear 71 a of the thirdtransmission gear body 71→the main transmission sub shaft 70→the frontgear 73 a of the first transmission gear body 73→the first-speed gear63→the front-gear-side interlocking connection member 67 b of the firsttransmission body 67→the slide connection member 67 d→the shaft-sideinterlocking connection member 67 a→the main-transmission main shaft 58thus performing the first transmission.

Here, the slide operation member 92 is engaged with the slide operationreceiving member 95 c of the first slide body 95 and, at the same time,the forming members 91 a, 91 b of the slide restricting body 91 areengaged with the slide operation receiving members 94 c, 93 c of thesecond, the third slide bodies 94, 93 so as to restrict the movement ofboth slide bodies 94, 93.

(Second Transmission Manipulation)

The main transmission lever 85 is rotatably manipulated in the rightwarddirection so as to rotate the operation member 85 a which is formed on alower-end portion of the main transmission lever 85 using the tiltingsupport member 87 as a fulcrum in the leftward direction. The rotationalforce is transmitted to the slide body support shaft 80 by way of theoperation receiving member 84→the lever interlocking shaft 81→theengaging member 82→the engaging member 83→the slide body support shaft80 thus rotating the slide body support shaft 80 in the clockwisedirection as viewed in a back view shown in FIG. 7, and, at the sametime, rotating the slide restricting body 91 in the clockwise directionby way of the slide operation member 92.

Subsequently, the main transmission lever 85 which is rotatablymanipulated in the rightward direction is further rotatably manipulatedin the frontward direction so as to allow the slide body support shaft80 to slide in the rearward direction.

Accordingly, the sliding force directed in the rearward direction of theslide body support shaft 80 is transmitted to the shift fork 94 b by wayof the slide operation member 92→the slide operation receiving member 94c of the second slide body 94→the boss portion 94 a→the shift fork 94 bso as to allow the slide connection member 66 d of the secondtransmission body 66 which is interlockingly connected to the shift fork94 b to slide from the neutral position to the rear slide transmissionposition thus establishing a state in which the shaft-side interlockingconnection member 66 a and the rear-gear-side interlocking connectionmember 66 c are interlockingly connected with each other.

As a result, the power which is transmitted from the engine 15 to theinner-side drive shaft 19 is transmitted to the main-transmission mainshaft 58 by way of the front split drive shaft member 30→the rear splitdrive shaft member 31→the fifth-speed gear 31 c→the front gear 71 a ofthe third transmission gear body 71→the main transmission sub shaft70→the rear gear 72 b of the second transmission gear body 72→thesecond-speed gear 62→the rear-gear-side interlocking connection member66 c of the second transmission body 66→the slide connection member 66d÷the shaft-side interlocking connection member 66 a→themain-transmission main shaft 58 thus performing the second transmission.

Here, the slide operation member 92 is engaged with the slide operationreceiving member 94 c of the second slide body 94 and, at the same time,the restricting member 91 b of the slide restricting body 91 is engagedwith the slide operation receiving members 95 c, 93 c of the first andthe third slide bodies 95, 93 so as to restrict the movement of bothslide bodies 95, 93.

(Third Transmission Manipulation)

The main manipulation lever 85 is rotatably manipulated in the rightwarddirection and, at the same time, is rotatably manipulated in therearward direction so as to allow the slide body support shaft 80 toslide in the front direction.

Accordingly, the sliding force directed to the frontward direction ofthe slide body support shaft 80 is transmitted to the shift fork 94 b byway of the slide operation member 92→the slide operation receivingmember 94 c of the second slide body 94→the boss portion 94 a→the shiftfork 94 b so as to allow the slide connection member 66 d of the secondtransmission body 66 which is interlockingly connected to the shift fork94 b to slide from the neutral position to the front slide transmissionposition thus establishing a state in which the shaft-side interlockingconnection member 66 a and the front-gear-side interlocking connectionmember 66 b are interlockingly connected with each other.

As a result, the power which is transmitted from the engine 15 to theinner-side drive shaft 19 is transmitted to the main-transmission mainshaft 58 by way of the front split drive shaft member 30→the rear splitdrive shaft member 31→the fifth-speed gear 31 c→the front gear 71 a ofthe first transmission gear body 71→the main transmission sub shaft70→the front gear 72 a of the second transmission gear body 72→thethird-speed gear 61→the front-gear-side interlocking connection member66 b of the second transmission body 66→the slide connection member 66d→the shaft-side interlocking connection member 66 a→themain-transmission main shaft 58 thus performing the third transmission.

Here, the slide operation member 92 is engaged with the slide operationreceiving member 94 c of the second slide body 94 and, at the same time,the restricting member 91 b of the slide restricting body 91 is engagedwith the slide operation receiving members 95 c, 93 c of the first andthe third slide bodies 95, 93 so as to restrict the movement of bothslide bodies 95, 93.

(Fourth Transmission Manipulation)

The main transmission lever 85 is rotatably manipulated in the leftwarddirection so as to rotate the operation member 85 a which is formed onthe lower-end portion of the main transmission lever 85 using thetilting support member 87 as a fulcrum in the rightward direction. Therotational force is transmitted to the slide body support shaft 80 byway of the operation receiving member 84→the lever interlocking shaft81→the engaging member 82→the engaging member 83→the slide body supportshaft 80 thus rotating the slide body support shaft 80 in thecounterclockwise direction as viewed in the back view shown in FIG. 7,and, at the same time, rotating the slide restricting body 91 in thecounterclockwise direction by way of the slide operation member 92.

Subsequently, the main transmission lever 85 which is rotatablymanipulated in the rightward direction is further rotatably manipulatedin the frontward direction so as to allow the slide body support shaft80 to slide in the rearward direction.

Accordingly, the sliding force directed in the rearward direction of theslide body support shaft 80 is transmitted to the shift fork 93 b by wayof the slide operation member 92→the slide operation receiving member 93c of the third slide body 93→the boss portion 93 a→the shift fork 93 bso as to allow the slide connection member 65 d of the thirdtransmission body 65 which is interlockingly connected to the shift fork93 b to slide from the neutral position to the rear slide transmissionposition thus establishing a state in which the shaft-side interlockingconnection member 65 a and the rear-gear-side interlocking connectionmember 65 c are interlockingly connected with each other.

As a result, the power which is transmitted from the engine 15 to theinner-side drive shaft 19 is transmitted to the main-transmission mainshaft 58 by way of the front split drive shaft member 30→the rear splitdrive shaft member 31→the fifth-speed gear 31 c→the rear gear 71 b ofthe third transmission gear body 71→the fourth-speed gear 62→therear-gear-side interlocking connection member 65 c of the thirdtransmission body 65→the slide connection member 65 d→the shaft-sideinterlocking connection member 65 a→the main-transmission main shaft 58thus performing the fourth transmission.

Here, the slide operation member 92 is engaged with the slide operationreceiving member 93 c of the third slide body 93 and, at the same time,the restricting member 91 a of the slide restricting body 91 is engagedwith the slide operation receiving members 95 c, 94 c of the first andthe second slide bodies 95, 94 so as to restrict the movement of bothslide bodies 95, 94.

(Fifth Transmission Manipulation)

The main manipulation lever 85 is rotatably manipulated in the leftwarddirection and, at the same time, is rotatably manipulated in therearward direction so as to allow the slide body support shaft 80 toslide in the frontward direction.

Accordingly, the sliding force directed to the frontward direction ofthe slide body support shaft 80 is transmitted to the shift fork 95 b byway of the slide operation member 92→the slide operation receivingmember 95 c of the third slide body 95→the boss portion 95 a→the shiftfork 95 b so as to allow the slide connection member 67 d of the thirdtransmission body 67 which is interlockingly connected to the shift fork95 b to slide from the neutral position to the front slide transmissionposition thus establishing a state in which the shaft-side interlockingconnection member 67 a and the front-gear-side interlocking connectionmember 67 b are interlockingly connected with each other.

As a result, the power which is transmitted from the engine 15 to theinner-side drive shaft 19 is transmitted to the main-transmission mainshaft 58 by way of the front split drive shaft member 30→the rear splitdrive shaft member 31→the fifth-speed gear 31 c→the front-gear-sideinterlocking connection member 65 b of the third transmission gear body67→the slide connection member 67 d→the shaft-side interlockingconnection member 65 a→the main-transmission main shaft 58 thusperforming the fifth transmission.

Here, the slide operation member 92 is engaged with the slide operationreceiving member 93 c of the third slide body 93 and, at the same time,the restricting member 91 a of the slide restricting body 91 is engagedwith the slide operation receiving members 95 c, 94 c of the first andthe second slide bodies 95, 94 so as to restrict the movement of bothslide bodies 95, 94.

(Backward Motion Changeover Manipulation)

The main transmission lever 85 is rotatably manipulated in the frontwarddirection in an approximately vertically erected state and the rotarymanipulation force is transmitted to the slide body support shaft 80 byway of the operation member 85 a which is formed on a lower-end portionof the main transmission lever 85→the operation receiving member 84→thelever interlocking shaft 81→the engaging member 82→the engaging member83→the slide body support shaft 80 so as to allow the slide body supportshaft 80 to slide in the rearward direction.

Accordingly, the sliding force of the slide body support shaft 80 in therearward direction is transmitted to the shift fork 95 b by way of theslide operation member 92→the slide operation receiving member 95 c ofthe third slide body 95→the boss portion 95 a→the shift fork 95 b and,thereafter, the slide connection member 67 d of the first transmissionbody 67 which is interlockingly connected with the shift fork 95 b isslid from the neutral position to the rear slide transmission positionthus establishing a state in which the shaft-side interlockingconnection member 67 a and the rear-gear-side interlocking connectionmember 67 c are interlockingly connected with each other.

As a result, the power transmitted from the engine 15 to the inner-sidedrive shaft 19 is transmitted to the main-transmission main shaft 58 byway of the front split drive shaft member 30→the rear split drive shaftmember 31→the fifth-speed gear 31 c→the front gear 71 a of the thirdtransmission gear body 71→the main transmission sub shaft 70→the reargear 73 b of the first transmission gear body 73→the counter gear 74→thebackward motion changeover gear 64→the rear-gear-side interlockinglyconnection member 67 c of the third transmission body 67→the slideconnection member 67 d→the shaft-side interlocking connection member 67a→the main-transmission main shaft 58 and hence, the main-transmissionmain shaft 58 is rotated reversely thus performing the backward motionchangeover.

Here, the slide operation member 92 is engaged with the slide operationreceiving member 95 c of the first slide body 95 and, at the same time,the forming members 91 a, 91 b of the slide restricting body 91 areengaged with the slide operation receiving members 94 c, 93 c of thesecond, the third slide bodies 94, 93 so as to restrict the movement ofboth slide bodies 94, 93.

[Casing Body]

The casing body 54 is, as shown in FIG. 2, FIG. 8 and FIG. 11, is formedin a cylindrical shape extending in the longitudinal direction, whereina shaft support wall 100 is formed on a middle portion of an innerperipheral surface. In the inside of the casing body 54, the subtransmission mechanism 47 is arranged at a position in front of theabove-mentioned shaft support wall 100 and, at the same time, adifferential mechanism 48 is arranged at a position behind the shaftsupport wall 100.

Further, with respect to the casing body 54 which is positioned in frontof the shaft support wall 100, an opening portion 101 is formed in theright side wall 54 b, the creep transmission part 49 described later isdetachably mounted by way of the opening portion 101, an opening portion102 is formed in a bottom portion 54 d, and a front-wheel-driving powertake out part 103 described later is mounted by way of the openingportion 102, and the creep transmission part 49 and thefront-wheel-driving power take out part 103 are respectivelyinterlockingly connected with the sub transmission mechanism 47.

Further, in the casing body 54 which is positioned behind the shaftsupport wall 100, as shown in FIG. 9, opening portions 104, 104 arerespectively formed in left and right side walls 54 a, 54 b, the rearaxle casings 8, 8 are communicably connected with each other by way ofthe respective opening portions 104, 104, rear axles 105, 105 whichextend in the lateral direction are inserted into and are rotatablysupported on the respective rear axle casings 8, 8, and the respectiverear axles 105, 105 are interlockingly connected with the differentialmechanism 48.

Further, with respect to the casing body 54 which is positioned behind ashaft support wall 100, as shown in FIG. 8, an opening portion 106 formaintenance is formed in a ceiling portion of the casing body 54 and theopening portion 106 is closed by a detachable lid body 107. A lift armsupport body 108 is formed in an upwardly bulging manner on a rearportion of the lid body 107, a lift arm support shaft 109 which has anaxis thereof directed in the lateral direction is inserted in and isrotatably supported on an upper portion of the lift arm support body108, and proximal end portions of a pair of left and right lift arms110, 110 are mounted on left and right side end portions of the lift armsupport shaft 109.

Further, as shown in FIG. 8, the PTO transmission part 6 is mounted inan opening 111 formed in a rear end of the casing body 54.

Further, as shown in FIG. 2 and FIG. 8, on rear lower portions of theleft and right side walls of the casing body 54, lower link connectionpins 112, 112 are formed in a state that the lower link connection pins112, 112 project outwardly, wherein front end portions of the pair ofleft and right lower links 13, 13 are rotatably supported on the casingbody 54 by way of the lower link connection pins 112, 112.

[Sub Transmission Mechanism]

In the sub transmission mechanism 47, as shown in FIG. 8, a subtransmission shaft 116 is interlockingly connected with a distal endportion (rear end portion) of the above-mentioned main-transmission mainshaft 58 by way of a planetary gear mechanism 115, and a distal endportion of the main-transmission main shaft 58 is extended rearwardlyand forms a sun gear 117 which constitutes a portion of a planetary gearmechanism 115. On the other hand, a sub transmission shaft 116 isarranged coaxially with the main-transmission main shaft 58, has amiddle portion thereof supported on a shaft support body 118 formed inthe inside of the casing body 54 by way of the bearing 119, and a distalend portion thereof supported on the above-mentioned shaft support wall100 by way of the bearing 120.

The planetary gear mechanism 115 is constituted as follows. A pair offront and rear inner gear support bodies 121, 122 which are formed in aring shape and are arranged around an outer periphery of the sun gear117 are mounted on the above-mentioned support wall forming body 55using mounting bolts 123 which have a longitudinally extending axis. Aninner gear 124 is supported between both inner gear support bodies 121,122 in a state that both ends of the inner gear 124 are supported byboth inner gear support bodies 121, 122. A plurality of planetary gears125 are arranged in the circumferential direction of the inner gear 124in a spaced-apart manner and, at the same time, the respective planetarygears 125 are meshed with both of the inner gear 124 and the sun gear117. A carrier 128 is mounted between inner peripheral portions of apair of front and rear inner gear support bodies 121, 122 by way of apair of front and rear bearings 126, 127, and the plurality of planetarygears 125 are integrally and interlockingly connected with the carrier128.

Further, the carrier 128 has a rear-end peripheral portion thereofextended in the more rearward direction than the bearing 127 positionedbehind the carrier 128 and forms a cylindrical gear forming member 129and the inner teeth 130 are formed on the inner-peripheral surface ofthe gear forming member 129 and, at the same time, forms the outer teeth131 as the creep drive gear on the outer peripheral surface of the gearforming member 129.

Still further, a cylindrical shift gear support body 132 is fittedbetween the outer peripheral surface of the sun gear 117 and the outerperipheral surface of the proximal-end portion (front end portion) 114of the sub transmission shaft 116 in a shiftable manner in the axialdirection by spline fitting and a front shift gear 133 is integrallyformed on the front outer peripheral surface of the shift gear supportbody 132 and, at the same time, a rear shift gear 134 is integrallyformed on the rear outer peripheral surface.

Then, as shown in FIG. 10 and FIG. 11, a fork support shaft 135 whoseaxis is directed in the longitudinal direction is arranged on the rightside in the inside of the casing body 54 and a proximal-end portion 137of a shift fork 136 is longitudinally slidably mounted on the forksupport shaft 135 and, at the same time, a distal-end portion 138 of theshift fork 136 is engaged with the shift gear support body 132.

Further, a boss portion 140 whose axis is directed in the lateraldirection is formed in the lid body 139 which constitutes a portion ofthe creep transmission part 49 described later and a lever support shaft141 passes through the boss portion 140 and a proximal-end portion ofthe sub transmission lever 142 is mounted on the outer peripheralportion of the lever support shaft 141 and, at the same time, aproximal-end portion of the interlocking arm 143 is mounted on theinner-end portion of the lever support shaft 141 and a proximal-endportion 137 of the above-mentioned shift fork 136 is connected to adistal end portion of the interlocking arm 143 by way of a block 144.

Due to such a constitution, by rotatably manipulating the subtransmission lever 142 in the longitudinal direction, the shift gearsupport body 132 is shifted in the longitudinal direction so as toperform the sub transmission manipulation.

That is, when the sub transmission lever 142 is rotated in the rearwarddirection, the interlocking arm 143 is rotated in the frontwarddirection by way of the lever support shaft 141 and the shift fork 136which is connected to a distal-end portion of the interlocking arm 143by way of the block 144 is slid in the frontward direction and hence,the shift gear support body 132 which is engaged with the shift fork 136is shifted in the frontward direction.

At this time, the shift gear support body 132 is shifted in a state thatthe shift gear support body 132 is extended between an outer peripheralsurface of the sun gear 117 and an outer peripheral surface of theproximal-end portion (front-end portion) 114 of the sub transmissionshaft 116 thus providing a state in which the sun gear 117 and the subtransmission shaft 116 are interlockingly connected with each other byway of the shift gear support body 132 (a state in which themain-transmission main shaft 58 and the sub transmission shaft 116 aredirectly connected with each other).

Accordingly, in such a shift position, the power is transmitted from thesun gear 117 which is integrally formed on the main-transmission mainshaft 58 to the sub transmission shaft 116 by way of the shift gearsupport body 132.

Further, when the sub transmission lever 142 is rotated in the frontwarddirection, the interlocking arm 143 is rotated in the rearward directionby way of the lever support shaft 141 and the shift fork 136 which isconnected to the distal-end portion of the interlocking arm 143 by wayof the block 144 is slid in the rearward direction and hence, the shiftgear support body 132 which is engaged with the shift fork 136 isshifted in the rearward direction.

Then, the shift gear support body 132 is detached from the outerperipheral surface of the sun gear 117 and is shifted on the outerperipheral surface of the proximal-end portion (front-end portion) 144of the sub transmission shaft 116 and, at the same time, the front shiftgear 133 is meshed with the inner teeth 130 which are formed on theinner peripheral surface of the gear forming member 129.

Accordingly, in such a shift position, rotation power of the sun gear117 which is integrally formed on the main-transmission main shaft 58 istransmitted to the proximal-end portion 114 of the sub transmissionshaft 116 by way of the planetary gear 125 which is meshed with the sungear 117→the carrier 128→the inner teeth 130 of the gear forming member129 which is integrally formed on the carrier 128→the front shift gear133 of the shift gear support body 132→the shift gear support body132→the proximal-end portion 114 of the sub transmission shaft 116.

At this time, the decelerated power is transmitted from themain-transmission main shaft 58 to the sub transmission shaft 116 by wayof the planetary gear mechanism 115 so as to perform the subtransmission.

Further, in this embodiment, when the sub transmission lever 142 isrotated in the further frontward direction, the creep transmission(ultra low speed transmission) is performed using the creep transmissionpart 49.

Here, to explain the creep transmission part 49, in the creeptransmission part 49, as shown in FIG. 8, FIG. 10 and FIG. 11, a lidbody 139 is detachably mounted on the opening portion 101 which isformed in the right wall of the above-mentioned casing body 54 using amounting bolt 145 so as to close the opening portion 101 and, at thesame time, the creep transmission mechanism 146 is detachably mounted onthe inner surface of the lid body 139.

Then, in the creep transmission mechanism 146, a gear support shaft 149whose axis is directed in the longitudinal direction is detachablyextended between a pair of front and rear shaft support members 147, 148which are formed in a projecting manner on the inner surface of the lidbody 139, a creep transmission gear body 151 is rotatably mounted on thegear support shaft 149 by way of a bearing 150 and a large-diameterinput gear 152 and a small-diameter output gear 153 are integrallyformed on the front portion and the rear portion of the creeptransmission gear body 151.

Further, the input gear 152 is detachably meshed with the outer teeth131 as a creep drive gear which is formed on the outer peripheralsurface of the gear forming member 129 and, at the same time, the outputgear 153 is detachably meshed with the creep power transmission gear 155which is rotatably mounted on the sub transmission shaft 116 by way of abearing 154. On a front surface of the creep power transmission gear155, a fitting-and-meshing gear 156 is formed in a state that the rearshift gear 134 which is integrally formed with a rear outer peripheralsurface of the shift gear support body 132 is fitted in and meshed withthe fitting-and-meshing gear 156.

Due to such a constitution, when the sub transmission lever 142 isrotated in furthest frontward position, the interlocking arm 143 isrotated in the rearward direction by way of the lever support shaft 141and the shift fork 136 which is connected with the distal-end portion ofthe interlocking arm 143 by way of the block 144 is slid in the rearwarddirection and hence, the shift gear support body 132 which is engagedwith the shift fork 136 is shifted to the maximum rearward position.

Then, the shift gear support body 132 is detached from the outerperipheral surface of the sun gear 117 and is shifted on the outerperipheral surface of the proximal-end portion (front-end portion) 114of the sub transmission shaft 116 and, at the same time, the rear shiftgear 134 is fitted in and meshed with the fitting in/meshing with gear156 which is formed on the front surface of the creep power transmissiongear 155.

Accordingly, in such a shift position, the rotation power of the sungear 117 which is integrally formed on the main-transmission main shaft58 is transmitted to the proximal-end portion 114 of the subtransmission shaft 116 by way of the planetary gear 125 which is meshedwith the sun gear 117→the carrier 128→the outer teeth 131 of the gearforming member 129 which is integrally formed on the carrier 128→theinput gear 156 of the creep transmission gear body 151→the output gear153 of the creep transmission gear body 151→the creep transmission gear155→the fitting in/meshed with gear 156→the rear shift gear 134 which isintegrally formed on the outer peripheral surface of the rear portion ofthe shift gear support body 132→the shift gear support body 132→theproximal-end portion 114 of the sub transmission shaft 116.

At this time, the power which is decelerated to ultra low speed istransmitted from the main-transmission main shaft 58 to the subtransmission shaft 116 by way of the planetary gear mechanism 115 andthe creep transmission mechanism 146 so as to perform the creeptransmission.

Here, since the input gear 152 of the creep transmission gear body 151is detachably meshed with the outer teeth 131 of the gear forming member129 which is integrally formed on the carrier 128 as the creep drivegear, it is possible to arranged the creep transmission mechanism 136 onthe peripheral portion of the planetary gear mechanism 115 in a compactmanner and hence, it is possible to prevent large-sizing of thetransmission portion 4.

Further, since the creep transmission manipulation can be also performedlinearly in the axial direction of the planetary gear mechanism 115, itis possible to simplify the transmission manipulation mechanism.

Further, the creep transmission part 49 is constituted by mounting thecreep transmission mechanism 146 on the lid body 139 and, at the sametime, the creep transmission part 49 is closed with the lid body 139 ina state that the lid body 139 is detachably mounted on the openingportion 101 formed in the casing body 54 and hence, it is possible toimprove the assembling property of the creep transmission part 49.

Further, when the creep specification is not necessary, in a state thatthe creep transmission mechanism 146 is removed from the lid body 139,the lid body 139 is mounted on the opening portion 101 of the casingbody 54, it is possible to easily change the specification from thecreep specification to the non-creep specification.

Further, when the creep specification is necessary, it is sufficient tomount the creep transmission mechanism 146 on the lid body 139 andhence, it is possible to easily perform the setting of the creepspecification and the non-creep specification.

A front-wheel-drive power takeout portion 103 is configured such that,as shown in FIG. 2 and FIG. 8, a takeout portion casing 160 is mountedon an opening portion 102 formed on a bottom portion of the casing body54 using mounting bolts 161, a front wheel drive shaft 164 which has anaxis thereof directed in the longitudinal direction is extended in theinside of the takeout portion casing 160 by way of a pair of front andrear bearings 162, 163, an input gear 165 is mounted on a middle portionof the front wheel drive shaft 164, and first and second intermediategears 167, 168 are interposed between the input gear 165 and the subtransmission shaft 116.

Here, the first intermediate gear 167 is rotatably mounted on aPTO-system power transmission shaft 169 described later by way of abearing 170 and, at the same time, the second intermediate gear 168 isrotatably mounted on a gear support shaft 173 by way of a bearing 174,wherein the gear support shaft 173 is extended between a pair of frontand rear gear support members 171, 172 which are formed in a state thatthe gear support members 171, 172 project toward the inside of thecasing body 54.

Further, the output gear 166, the first intermediate gear 167, thesecond intermediate gear 168 and the input gear 165 are interlockinglyconnected with each other by allowing these gears to be meshed with eachother in series.

Further, the front wheel drive shaft 164 has a distal-end portion 175thereof projected frontwardly from the takeout portion casing 160 andthe distal end portion 175 thereof interlockingly connected with aninput shaft (not shown in the drawing) provided to a front axle casingby way of a power transmission shaft or the like.

In this manner, a rotational force of the sub transmission shaft 116 istransmitted to the front wheels 7, 7 by way of the output gear 166mounted on the sub transmission shaft 116→the first intermediate gear167→the second intermediate gear 168→the input gear 165→the front wheeldrive shaft 164→the power transmission shaft and the like→the inputshaft→the front axle→the front wheels 7, 7 thus enabling the four-wheeldrive traveling.

Further, in this embodiment, the input gear 165 is engaged with a middleportion of the front wheel drive shaft 164 by spline fitting, whereinthe input gear 165 is shiftable between a position at which the inputgear 165 is meshed with the second intermediate gear 168 and a positionat which such meshing is released and, at the same time, the shiftingmanipulation of the input shaft 165 is performed from the outside of thetakeout part casing 160 using a shift manipulation mechanism (not shownin the drawing).

By performing the shifting manipulation which allows the input gear 165to be meshed with the second intermediate gear 168 in this manner, it ispossible to perform the four-wheel drive traveling as described aboveand, at the same time, by performing the shifting manipulation whichreleases the meshing of the input gear 165 with the second intermediategear 168, it is possible to perform the two wheel drive traveling whichdrives only the rear wheels whereby it is possible to efficientlyperform a work by suitably performing the changeover manipulation of thefour-wheel drive traveling and the two-wheel drive travelingcorresponding to the work condition.

[Differential Mechanism]

The differential mechanism 48 is, as shown in FIG. 8 and FIG. 9,interposed between the above-mentioned sub transmission shaft 116 andthe pair of left and right rear axles 105, 105, wherein on a distal-endportion (a rear-end portion) of the sub transmission shaft 116 which isextended rearwardly than the shaft support wall 100, an output bevelgear 180 is integrally formed, while rear axle input gears 181, 181 aremounted on proximal end portions of respective rear axles 105, 105, andthe output bevel gear 180 is interlockingly connected with therespective rear axle input gears 181, 181 by way of the differentialmechanism 48.

That is, the differential mechanism 48 is configured such that a largedeceleration gear 183 which is meshed with the above-mentioned outputbevel gear 180 is mounted on an outer peripheral surface of thedifferential casing 182, while in the inside of the differential casing182, a pair of front and rear small differential gears 185, 185 arerotatably mounted by way of a small differential gear support shaft 184which extends longitudinally and, at the same time, a pair of left andright large differential gears 187, 187 are mounted by way of a pair oflarge differential gear support shafts 186, 186 which extend in thelateral direction, and the respective large differential gears 187, 187are meshed with both small differential gears 185, 185.

Further, in cylindrical communication connecting members 188, 188 whichare integrally formed with left and right side portions of thedifferential casing 182, a pair of left and right cylindrical shaftsupport bodies 189, 189 which direct axes thereof in the lateraldirection are detachably fitted in a state that the cylindrical shaftsupport bodies 189, 189 are communicably connected with each other. Inthe inside of the respective cylindrical shaft support bodies 189, 189which are allowed to pass through the respective cylindricalcommunication connecting members 188, 188, the above-mentioned largedifferential gear support shafts 186, 186 are inserted and supported. Onportions of the respective large differential gear support shafts 186,186 which project from the cylindrical shaft support bodies 189, 189,power transmission gears 190, 190 which are respectively meshed with theabove-mentioned rear axle input gears 181, 181 are mounted. Further,distal end portions of the respective large differential gear supportshafts 186, 186 are detachably connected with traveling brakes 192, 192of brake portions 191, 191 described later.

In this manner, a rotational force which is transmitted to the subtransmission shaft 116 is transmitted to the respective rear wheels 9, 9by way of the output bevel gear 180 which is integrally formed with thedistal-end portion (rear-end portion) of the sub transmission shaft116→the large deceleration gear 183→the differential casing 182→thesmall differential gear support shaft 184→the respective smalldifferential gears 185, 185→the respective large differential gears 187,187→the respective large differential gear support shafts 186, 186→therespective power transmission gears 190, 190→the respective rear axleinput gears 181, 181→the respective rear axles 105, 105→the respectiverear wheels 9, 9.

Further, the pair of left and right cylindrical shaft support bodies189, 189 are fitted into mounting opening portions 194, 194 which areformed in left and right side walls 54 a, 54 b of the casing body 54from the outside and, at the same time, the cylindrical shaft supportbodies 189, 189 are detachably mounted on the left and right side walls54 a, 54 b using mounting bolts 195, 195, while the differential casing182 is detachably extended between both cylindrical shaft support bodies189, 189.

Further, by pulling out the respective cylindrical shaft support bodies189, 189 from the mounting opening portions 194, 194 to the outsideafter removing the mounting bolts 195, 195, it is possible to remove therespective cylindrical shaft support bodies 189, 189 from the casingbody 54. In such an operation, it is also possible to remove therespective large differential gear support shafts 186, 186 by pullingout the respective large differential gear support shafts 186, 186 fromthe differential casing 182 integrally with the respective cylindricalshaft support bodies 189, 189.

Accordingly, the differential casing 182 which is detachably extendedbetween both cylindrical shaft support bodies 189, 189 can be, afterremoving the respective cylindrical shaft support bodies 189, 189, takenout from the opening portion 106 for maintenance which is formed in theceiling portion of the casing body 54.

Further, in the brake portion 191, a traveling brake 192 is arranged inthe inside of a brake casing 196, and the traveling brake 192 performsthe braking/releasing by manipulation of a brake manipulation lever 198by way of a brake operation member 197. Numeral 199 indicates a brakelever support shaft which is pivotally supported on the brake casing196.

Then, the brake casing 196 is detachably mounted between a side wall ofthe casing body 54 and a base portion of an outer peripheral surface ofthe rear axle casing 8 in a state that the brake casing 196 is extendedtherebetween. By removing the brake casing 196 from the casing body 54and the rear axle casing 8, it is possible to remove the traveling brake192 from a distal-end portion of the large differential gear supportshaft 186 integrally with the brake casing 196.

In this manner, the differential mechanism 48 can selectively adopteither one of a mounting mode in which, as shown in FIG. 9(a), the largereduction gear 183 is meshed with the output bevel gear 180 from theright side and the mounting mode in which, as shown in FIG. 9(b), thelarge speed-reduction gear 183 is meshed with the output bevel gear 180from the left side in a state that the differential mechanism 48 isvertically reversed to change over left and right portions of thedifferential mechanism 48.

Accordingly, corresponding to an operation machine which is connected tothe tractor A or an operation form, the advancing direction (mainoperation direction) of the tractor A can be easily changed by selectingthe mounting form of the differential mechanism 48.

Next, the constitution of the PTO transmission part 6 is explained withreference to FIG. 8, FIG. 10 and FIG. 11.

That is, in the PTO transmission part 6, as shown in FIG. 8, FIG. 10 andFIG. 11, a PTO casing 200 is detachably mounted in the opening portion111 which is formed in the rear end of the casing body 54 and a PTOtransmission mechanism 201 is arranged in the inside of the PTO casing200.

Then, the PTO casing 200 is formed of a front casing forming body 202which is arranged in the inside of the casing body 54 in an accommodatedmanner and a rear casing forming body 203 which is arranged in anexpanding manner in the rearward direction from the casing body 54. Aflange-like mounting member 204 is integrally formed on the front-endperipheral portion of the rear casing forming body 203 and the mountingmember 204 is brought into contact with the rear-end peripheral portionof the casing body 54 from behind and, at the same time, is mounted onthe rear-end peripheral portion of the casing body 54 by a mounting bolt205 whose axis is directed in the longitudinal direction.

In this manner, since the PTO casing 200 is detachably mounted in theopening portion 111 which is formed in the rear end of the casing body54, it is possible to easily perform the assembling operation and themaintenance operation of the PTO transmission mechanism 201 which isaccommodated in the inside of the PTO casing 200.

Here, a top link bracket 206 for pivotally supporting and connecting afront-end portion of the top link 12 is mounted between a rear portionof the above-mentioned lift arm support body 108 and an upper portion ofa rear-end peripheral portion of the casing body 54. The top linkbracket 206 is formed of a plate-like mounting seat 207 whose surface isbrought into contact with the rear portion of the lift arm support body108 and the upper portion of the rear-end peripheral portion of thecasing body 54 and is to be mounted using a mounting bolt 210 and a pairof left and right plate-like pivotally-supporting/connecting members208, 208 which are formed in a state that thepivotally-supporting/connecting members 208, 208 project in the morerearward direction than the rear surface of the mounting seat 207.Numeral 209 indicates a connection hole.

Then, the lower portion of the mounting seat 207 is brought into contactwith and is overlapped to the mounting member 204 of the rear casingforming body 203 from behind and, at the same time, the lower portion ofthe mounting seat 207 and the mounting member 204 of the rear casingforming body 203 are fastened together using a mounting bolt 205.

Further, lift cylinder support shafts 211, 211 as lift cylinder mountingportions are formed on left and right side walls of the rear casingforming body 203 in a state that the lift cylinder support shafts 211,211 project toward the outside. Lift cylinders 212, 212 which areextended or contracted in the vertical direction are disposed betweenthe respective lift cylinder support shafts 211, 211 and middle portionsof the above-mentioned lift arms 110, 110. Numeral 213 indicates a liftcylinder connection pin and numeral 214 indicates a lift cylinderpivotally-supporting connection member.

In this manner, a pair of left and right lift cylinders 212, 212 whichare operated in a vertically stretching manner are arranged at left andright side positions of the rear casing forming body 203 and, at thesame time, the lower-end portions of the respective lift cylinders 212,212 are supported on the rear casing forming body 203 by way of the lintcylinder support shafts 211, 211 and hence, it is possible to facilitateto set positions of both of the lift cylinders 212, 212 arrangedvertically or approximately vertically. Accordingly, strokes of therespective lift cylinders 212, 212 can be made small and hence, it ispossible to make the sizes of the respective lift cylinders 212, 212small and, besides, it is possible to reduce the power loss.

Further, since the lower-end portions of the respective lift cylinders212, 212 are supported on the rear casing forming body 203 by way of thelift cylinder support shafts 211, 211, it is possible to firmly supportthe respective lift cylinders 212, 212.

Further, for example, by reducing the width in the lateral direction ofthe rear casing forming body 203 and arranging the pair of left andright lift cylinders 212, 212 at the left and right side positions ofthe rear casing forming body 203 and, at the same time, arranging thepair of left and right lift cylinders 212, 212 within the width in thelateral direction of the casing body 54, it is possible to increase theflexibility of the mounting position of a vertically movable linkmechanism on the casing body 54.

Next, to explain the PTO transmission mechanism 201, in the PTOtransmission mechanism 201, as shown in FIG. 8, an input shaft 220, atransmission shaft 221 and a PTO shaft 222 whose axes are directed inthe longitudinal direction are rotatably supported in the inside of thePTO casing 200 by way of bearings 223, 224, 225, 226, 227, 228respectively. The input shaft 220 has a distal-end portion 240 thereofprojected in the frontward direction from an input shaft projectionportion 239 which is formed on a front wall of the PTO casing 200, whilethe PTO shaft 222 has a distal-end portion 242 thereof projected in therearward direction from a PTO shaft projection portion 241 which isformed on a rear wall of the PTO casing 200.

Then, an output gear 229 is formed on the input shaft 220, while alarge-diameter input gear 230, a first transmission gear 231 and asecond transmission gear 232 are coaxially mounted on the transmissionshaft 221 and the above-mentioned large-diameter input gear 230 ismeshed with the above-mentioned output gear 229.

Further, a shift gear body 233 is fitted on the PTO shaft 222 by splinefitting in a state that the shift gear body 233 is slidable in ashiftable manner in the axial direction and, at the same time, an inputgear 235 is rotatably mounted on the PTO shaft 222 by way of a bearing234 and a large-diameter shift gear 236 and a small-diameter shift gear237 are mounted on the shift gear body 233, while a fitting-and-meshinggear 238 is formed on a front surface of the input gear 235 in a statethat the above-mentioned small-diameter shift gear 237 is fitted in andmeshed with the fitting-and-meshing gear 238.

Due to such a constitution, by shifting the shift gear 233 using the PTOtransmission manipulation mechanism not shown in the drawing, it ispossible to perform the first PTO transmission manipulation which allowsthe large-diameter shift gear 236 to be meshed with the above-mentionedfirst transmission gear 231 and the second PTO transmission manipulationwhich allows the small-diameter shift gear 237 to be fitted in andmeshed with the fitting and meshing gear 238.

Further, the distal-end portion 240 of the input shaft 220 is, as shownin FIG. 3, interlockingly connected with the above-mentioned outer driveshaft 20 by way of a PTO system power transmission shaft 169 so as toconstitute the PTO system power transmission mechanism 52. The PTOsystem power transmission shaft 169 is arranged in the inside of thetransmission casing 45 from the front portion to the rear portion withan axis thereof directed in the longitudinal direction.

That is, the PTO system power transmission shaft 169 is, as shown inFIG. 3, formed by connecting first to fourth split power transmissionshafts 245, 246, 247, 248 in the longitudinal direction.

Then, the first split power transmission shaft 245 is, as shown in FIG.3 and FIG. 5, rotatably extended between the rear wall 27 of the clutchhousing 17 and the above-mentioned inner support wall 57 by way ofbearings 249, 250. An input gear 244 is formed on the middle portion ofthe first split power transmission shaft 245 and the input gear 244 ismeshed with the PTO drive gear 20 c.

Further, in the second split power transmission shaft 246, as shown inFIG. 3 and FIG. 5, a middle portion thereof is rotatably supported onthe above-mentioned support wall forming body 55 by way of a bearing 251and, at the same time, a front-end portion thereof is connected with arear-end portion of the above-mentioned first split power transmissionshaft 245 by way of a first cylindrical connection body 252.

In the third split power transmission shaft 247, as shown in FIG. 3 andFIG. 8, a middle portion thereof is rotatably supported on the shaftsupport body 118 by way of a bearing 253 and, at the same time, afront-end portion thereof is connected with a rear-end portion of theabove-mentioned second split power transmission shaft 246 by way of asecond cylindrical connection body 254.

In the fourth split power transmission shaft 248, as shown in FIG. 3 andFIG. 8, a front-end portion thereof is connected with a rear-end portionof the above-mentioned third split power transmission shaft 247 by wayof a one way clutch 255 and, at the same time, a rear-end portionthereof is connected with a distal-end portion 240 of theabove-mentioned input shaft 220 by way of a third cylindrical connectionbody 256.

Here, the one way clutch 255 is formed of a front clutch forming body257 which is mounted on the rear-end portion of the third split powertransmission shaft 247 and a rear clutch forming body 258 which ismounted on the front-end portion of the fourth split power transmissionshaft 248. A meshing member 259 which is formed in a projecting manneron a rear surface of the front clutch forming body 257 and a meshingmember 260 which is formed in a projecting manner on a front surface ofthe rear clutch forming body 258 are meshed with each other in alongitudinally facing manner so that, in the right rotation, both of themeshing members 259, 260 are engaged and the third and the fourth splitpower transmission shafts 247, 248 are integrally rotated in the rightrotational direction, while, in the reverse rotation, both of themeshing members 259, 260 are not engaged with each other.

In this manner, the power transmitted from the engine 15 to the outerdrive shaft 20 is transmitted to the input shaft 220 by way of the PTOdrive gear 20c which is integrally formed on the outer drive shaft20→the input gear 244→the first split power transmission shaft 245→thefirst cylindrical connection body 252→the second split powertransmission shaft 246→the second cylindrical connection body 254→thethird split power transmission shaft 247→the one way clutch 255→thefourth split power transmission shaft 248→the third cylindricalconnection body 256→the input shaft 220.

Then, when the PTO transmission mechanism 201 performs the first PTOtransmission manipulation, the power transmitted to the input shaft 220is transmitted to the PTO shaft 222 by way of the output gear 229→thelarge-diameter input gear 230→the transmission shaft 221→the firsttransmission gear 231→the large-diameter shift gear 236 of the shiftgear body 233→the input shaft 220, and the power is taken out from thePTO shaft 222 so as to drive the respective operation machines.

Further, when the PTO transmission mechanism 201 performs the second PTOtransmission manipulation, the power transmitted to the input shaft 220is transmitted to the PTO shaft 222 by way of the output gear 229→thelarge-diameter input gear 230→the transmission shaft 221→the secondtransmission gear 232→the input gear 235→the small-diameter shift gear237 of the shift gear body 233→the PTO shaft 222 and, the power is takenout from the PTO shaft 222 so as to drive the respective operationmachines.

At this time, even when the PTO shaft 222 is reversely rotated inresponse to loads from the respective operation machines and the poweris transmitted to the fourth split power transmission shaft 248 by wayof the input shaft 220→the third cylindrical connection body 256→thefourth split power transmission shaft 248, since the one way clutch 255is interposed between the fourth split power transmission shaft 248 andthe third split power transmission shaft 247, the power is nottransmitted from the fourth split power transmission shaft 248 to thethird split power transmission shaft 247.

Accordingly, it is possible to prevent a drawback that the travelingsystem power transmission mechanism 51 is damaged or the like due to thefact that the power is transmitted backward from the PTO shaft 222 tothe traveling system power transmission mechanism 51, from the maintransmission mechanism 46 down.

Particularly, as shown in FIG. 12, since, in the clutch portion 3designed in single clutch, the input gear 244 which is formed on thefirst split power transmission shaft 245 is meshed with a PTO drive gear300 which is formed on the rear split drive shaft member 31, it ispossible to surely prevent the case in which the power is transmittedbackward to the main-transmission main shaft 58 by way of the firstsplit power transmission shaft 245→the input gear 244→the PTO drive gear300→the rear split drive shaft member 31 using the one way clutch255→the main-transmission main shaft 58.

Then, by arranging the one way clutch 255 in the inside of the casingbody 54, in performing the changeover of the specification between adouble-clutch specification which uses the traveling clutch 21 and thePTO clutch 22 as shown in FIG. 8 and a single clutch specification whichuses only the traveling clutch 21 as shown in FIG. 12, it is possible toeasily change over the clutch specification by merely replacing only theclutch portion 3 while maintaining the inside of the transmission casing45 as it is as a common portion.

FIG. 13 is a view showing the sub transmission mechanism 47 as anotherembodiment. The sub transmission mechanism 47 is constituted byinterlockingly connecting the sub transmission shaft 116 to a distal-endportion (rear-end portion) of the main-transmission main shaft 58 by wayof a sub transmission planetary gear mechanism 265 and a creeptransmission planetary gear mechanism 266. The distal-end portion of themain-transmission main shaft 58 is extended in the rearward direction toform a sun gear 267 which constitutes a portion of the sub transmissionplanetary gear mechanism 265 and, at the same time, an intermediateshaft 269 is arranged between the main-transmission main shaft 58 andthe sub transmission shaft 116 on the same axis by way of a planetarygear mechanism support body 268 and a distal end portion of theintermediate shaft 269 forms a sun gear 270 which constitutes a portionof the creep transmission planetary gear mechanism 266.

The sub transmission planetary gear mechanism 265 is constituted in afollowing manner. That is, an inner gear support body 273 which isformed in a ring shape and is arranged on the outer periphery of the sungear 267 is mounted on the above-mentioned support wall forming body 55using a mounting bolt 274 whose axis is directed in the longitudinaldirection. An inner gear 275 is supported in a cantilever style at theinner gear support body 273 and a plurality of planetary gears 276 arearranged on the inner gear 275 in a spaced-apart manner in thecircumferential direction and, at the same time, the respectiveplanetary gears 276 are meshed with both of the inner gear 275 and thesun gear 270, while a carrier 277 is mounted on the inner peripheralportion of the inner-gear support body 273 and the plurality ofplanetary gears 276 are integrally and interlockingly connected with thecarrier 277.

Further, in the carrier 277, a rear-end peripheral portion thereof isextended in the rearward direction to form a cylindrical gear formingmember 278 and inner teeth 279 are formed on an inner-peripheral surfaceof the gear forming member 278.

Still further, the cylindrical shift gear support body 281 is fittedbetween an outer-peripheral surface of the sun gear 267 and anouter-peripheral surface of a proximal-end portion (front-end portion)280 of the intermediate shaft 269 in a shiftable manner by splinefitting in the axial direction and a shift gear 282 is integrally formedon a front outer-peripheral surface of the shift gear support body 281.

The creep transmission planetary gear mechanism 266 is constituted in afollowing manner. That is, an inner gear support body 283 which isformed in a ring shape and arranged on the outer periphery of the sungear 270 is mounted on the above-mentioned planetary gear mechanismsupport body 268 using a mounting bolt 284 whose axis is directed in thelongitudinal direction. An inner gear 285 is supported in a cantileverstyle at the inner gear support body 283 and a plurality of planetarygears 286 are arranged on the inner gear 285 in a spaced-apart manner inthe circumferential direction and, at the same time, the respectiveplanetary gears 286 are meshed with both of the inner gear 285 and thesun gear 270, while a carrier 287 is mounted on the inner-peripheralportion of the inner-gear support body 283 and the plurality ofplanetary gears 286 are integrally and interlockingly connected with thecarrier 287.

Further, in the carrier 287, a rear-end portion thereof is extended inthe rearward direction to form a cylindrical gear forming member 288 andinner teeth 289 are formed in an inner peripheral surface of the gearforming member 288.

Still further, the cylindrical shift gear support body 290 is fittedbetween an outer peripheral surface of the sun gear 270 and an outerperipheral surface of a proximal-end portion (front-end portion) 114 ofthe sub transmission shaft 116 in a shiftable manner by a spline fittingin the axial direction and a shift gear 291 is integrally formed on afront outer-peripheral surface of the shift gear support body 290.

In this manner, by rotatably manipulating a sub transmission lever notshown in the drawing in the longitudinal direction, the shit gearsupport body 281 is shifted in the longitudinal direction so as toperform the sub transmission manipulation.

That is, when the sub transmission lever is rotated in the rearwarddirection, the shift gear support body 281 is shifted to a state inwhich the shift gear support body 281 crosses over between the outerperipheral surface of the sun gear 267 and the outer peripheral surfaceof the proximal-end portion (front-end portion) 280 of the intermediateshaft 269 and hence, it becomes a state in which the sun gear 267 andthe intermediate shaft 269 are interlockingly connected by way of theshift gear support body 281 (a state in which the main-transmission mainshaft 58 and the intermediate shaft 269 are directly connected).

Accordingly, in such a shift position, power is transmitted from the sungear 267 which is integrally formed on the main-transmission main shaft58 to the intermediate shaft 269 by way of the shift gear support body281.

Further, when the sub transmission lever is rotated in the frontwarddirection, the shift gear support body 281 is detached from anouter-peripheral surface of the sun gear 267 and is shifted to theouter-peripheral surface of the proximal-end portion (front-end portion)280 of the intermediate shaft 269 and, at the same time, the shift gear282 is meshed with the inner teeth 279 which are formed on the innerperipheral surface of the shift gear forming member 278.

Accordingly, the rotation power of the sun gear 267 which is integrallyformed on the main-transmission main shaft 58 is transmitted to theproximal-end portion 280 of the intermediate shaft 269 by way of theplanetary gear 276 which is meshed with the sun gear 267→the carrier277→the inner teeth 279 of the gear forming member 278 which isintegrally formed on the carrier 277→the shift gear 282 of the shiftgear support body 281→the shift gear support body 281→the proximal-endportion 280 of the intermediate shaft 269.

Here, decelerated power is transmitted from the main-transmission mainshaft 58 to the intermediate shaft 269 by way of the planetary gearmechanism 265 so as to perform the sub transmission.

Then, the shift gear support body 290 of the creep transmissionplanetary gear mechanism 266 is shifted to a state in which the shiftgear support body 290 crosses over between the outer peripheral surfaceof the sun gear 270 and the outer peripheral surface of the proximal-endportion (front-end portion) 114 of the sub transmission shaft 116 andhence, it becomes a state in which the sun gear 270 and the subtransmission shaft 116 are interlockingly connected by way of the shiftgear support body 290.

Accordingly, in such a shift position, power is transmitted withoutbeing decelerated from the sun gear 267 which is integrally formed onthe main-transmission main shaft 58 to the intermediate shaft 269 by wayof the shift gear support body 281 and hence, the creep transmission(ultra low speed transmission) is not performed.

Further, in this embodiment, when the sub transmission lever not shownin the drawing is further rotated in the forward direction, the creeptransmission (ultra low speed transmission) is performed using the creeptransmission planetary gear mechanism 266.

That is, when the sub transmission lever is further rotated in theforward direction, the shift gear support body 281 is detached from theouter peripheral surface of the sun gear 267 and is shifted to the outerperipheral surface of the proximal-end portion (front-end portion) 114of the sub transmission shaft 116 and, at the same time, the shift gear282 is meshed with the inner teeth 289 which are formed on the innerperipheral surface of the gear forming member 288.

Accordingly, the rotation power of the sun gear 270 which is integrallyformed on the intermediate shaft 269 is transmitted to the proximal-endportion 114 of the sub transmission shaft 116 by way of the planetarygear 286 which is meshed with the sun gear 270→the carrier 287→the innerteeth 289 of the gear forming member 288 which is integrally formed onthe carrier 287→the shift gear 291 of the shift gear support body290→the shift gear support body 290→the proximal-end portion 114 of thesub transmission shaft 116.

Here, decelerated power is transmitted from the intermediate shaft 269to the sub transmission shaft 116 by way of the planetary gear mechanism266 so as to perform the creep transmission (ultra low speedtransmission).

Further, FIG. 14 is a view showing the sub transmission mechanism 47 asstill another embodiment. The sub transmission mechanism 47 isconstituted by interlockingly connecting the sub transmission shaft 116to a distal-end portion (rear-end portion) of the main-transmission mainshaft 58 by way of the planetary gear mechanism 265 and has the samebasic constitution as the constitution of the sub transmission mechanism47 of the above-mentioned embodiment. However, the constitution of thesub transmission mechanism 47 of this embodiment substantially differsfrom the constitution of the sub transmission mechanism 47 of theabove-mentioned embodiment in that the sub transmission mechanism 47 ofthis embodiment is not provided with the creep transmission planetarygear mechanism 266 and the intermediate shaft 269 and has no creeptransmission function.

That is, in the sub transmission planetary gear mechanism 265, thecylindrical shift gear support body 281 is fitted between the outerperipheral surface of the sun gear 267 and the outer peripheral surfaceof the proximal-end portion (front-end portion) 114 of the subtransmission shaft 116 in a shiftable manner in the axial direction byspline fitting and the shift gear 282 is integrally formed on the frontouter-peripheral surface of the shift gear support body 281.

Then, by rotatably manipulating the sub transmission lever not shown inthe drawing in the longitudinal direction, the shit gear support body281 is shifted in the longitudinal direction so as to perform the subtransmission manipulation.

In this manner, when the sub transmission lever is rotated in therearward direction, the shift gear support body 281 is shifted to thestate in which the shift gear support body 281 crosses over between theouter peripheral surface of the sun gear 267 and the outer peripheralsurface of the proximal-end portion (front-end portion) 114 of the subtransmission shaft 116 and hence, it becomes a state in which the sungear 267 and the sub transmission shaft 116 are interlockingly connectedby way of the shift gear support body 281 (a state in which themain-transmission main shaft 58 and the sub transmission shaft 116 aredirectly connected).

Accordingly, in such a shift position, power is transmitted from the sungear 267 which is integrally formed on the main-transmission main shaft58 to the sub transmission shaft 116 by way of the shift gear supportbody 281.

Further, when the sub transmission lever is rotated in the frontwarddirection, the shift gear support body 281 is detached from anouter-peripheral surface of the sun gear 267 and is shifted to theouter-peripheral surface of the proximal-end portion (front-end portion)114 of the sub transmission shaft 116 and, at the same time, the shiftgear 282 is meshed with the inner teeth 279 which are formed on theinner peripheral surface of the shift gear forming member 278.

Accordingly, in such a shift position, the rotation power of the sungear 267 which is integrally formed on the main-transmission main shaft58 is transmitted to the proximal-end portion (front-end portion) 114 ofthe sub transmission shaft 116 by way of the planetary gear 276 which ismeshed with the sun gear 267→the carrier 277→the inner teeth 279 of thegear forming member 278 which is integrally formed on the carrier277→the shift gear 282 of the shift gear support body 281→the shift gearsupport body 281→the proximal-end portion (front-end portion) 114 of thesub transmission shaft 116.

Here, decelerated power is transmitted from the main-transmission mainshaft 58 to the sub transmission shaft 116 by way of the planetary gearmechanism 265 so as to perform the sub transmission.

INDUSTRIAL APPLICABILITY

(1) According to the present invention described in claim 1, the PTOcasing which incorporates the PTO transmission mechanism therein isdetachably mounted on the rear portion of the transmission casing and,at the same time, the PTO casing is mounted in a state that the frontportion thereof is housed in the inside of the transmission casing.

By detachably mounting the PTO casing which incorporates the PTOtransmission mechanism therein on the rear portion of the transmissioncasing in this manner, it is possible to easily perform the assemblingoperation and the maintenance operation of the PTO transmissionmechanism.

Further, by mounting the PTO casing in a state that the front portionthereof is housed in the inside of the transmission casing, it ispossible to miniaturize the transmission casing (make the transmissioncasing compact).

(2) According to the present invention described in claim 2, theproximal end portion of the lift cylinder is pivotally mounted on theupper portion of the transmission casing, the lift cylinder mountingportion is formed on the lower portion of the side wall of the PTOcasing, and the lift cylinder which performs theextension-and-contraction movement is interposed between the liftcylinder mounting portion and the middle portion of the lift arm.

In this manner, by forming the lift cylinder mounting portion on thelower portion of the side wall of the PTO casing which is mounted on therear portion of the transmission casing and by interposing the liftcylinder between the lift cylinder mounting portion and the middleportion of the lift arm, it is possible to allow the lift cylinder totake the vertical or substantially vertical posture and hence, thestroke of the lift cylinder is made small whereby the lift cylinder canbe miniaturized and, at the same time, the power loss can be made small.

1. A tractor which is characterized in that a PTO casing whichincorporates a PTO transmission mechanism therein is detachably mountedon a rear portion of a transmission casing and, at the same time, thePTO casing is mounted in a state that a front portion thereof is housedin the inside of the transmission casing.
 2. A tractor according toclaim 1, wherein a proximal end portion of the lift cylinder ispivotally mounted on an upper portion of the transmission casing, a liftcylinder mounting portion is formed on a lower portion of a side wall ofthe PTO casing, and a lift cylinder which performs anextension-and-contraction movement in the vertical direction isinterposed between the lift cylinder mounting portion and a middleportion of the lift arm.